Digital cameras don't have the dynamic range of your eye, or even film, and although large-sensor cameras do better than small-sensor cameras in this respect, the problem will still exist. So while your slide might have captured the scene more or less as you saw it, photographing that high contrast slide with a digital camera will produce a disappointing result.
Here's an example of a high-contrast scene, originally shot on Fujichrome Sensia 100, handheld, through a living room window. The following images were taken with the same digitizing setup described previously.
This photo was under-exposed 2 stops (-2ev) showing the foliage clearly, but
leaving the car abnormally dark:
This photo was evenly exposed (0ev) brightening the car a bit, but blowing
out some of the foliage:
This photo was over-exposed 2 stops (+2ev) showing the car clearly, but
almost completely blowing out the foliage:
None of the above photos match the slide, or look very natural, and they are all disappointing for different reasons. The solution is HDR (high dynamic range) software.
The product I chose was easyHDR, but there are many others, some standalone, and some built into comprehensive photo editing suites. They all work the same way though: you take a series of photos at different exposures, load them into the software, and click a few buttons. (There are plenty of online tutorials that explain this in more detail, and the easyHDR website also has one.)
The following image was produced using easyHDR's default settings, and it is virtually identical to the slide:
There was only one small problem that I discovered. These 100% crops of the headrest area (HDR output on the right) show some minor halo and purple fringing. It's likely that these effects could be reduced or eliminated with a bit of adjustment, but for my purposes it's not an issue.
The freeware version of easyHDR does not support batch processing, but if you only have a few slides to do, that isn't necessary. However, if you have a very large slide collection, or want to do this for others, then it would be worthwhile purchasing the full version. If your camera supports 2ev AEB, you could easily and quickly take bracketed photos of all your slides, process everything through HDR, then choose which ones you want to keep.
Regardless of which procedure you use, HDR solves the nagging problem of dynamic range, and handily complements the do-it-yourself slide digitizing process.